Golf Club Head Having Center of Gravity Offset

ABSTRACT

The present invention is directed to golf club apparatus and processes. A golf club with a center of gravity offset comprises a shaft presenting a central axis and a club head having a face and a hosel. The club head defines a first axis generally parallel to the face and collinear with the hosel. The shaft is joined to the club head at the hosel, with the shaft and hosel defining a second axis. The club head has a center of gravity configured proximate the intersection of the first axis and the second axis.

PRIORITY

The present invention claims priority to provisional application62/000,934, which has a filing date of May 20, 2014.

BACKGROUND

1. Field of the Invention

The present application is directed to a golf club head, particularly agolf club having a configured center of gravity.

2. Description of the Related Art

A golf club is made of a grip, a shaft, and a club head. A golf clubshaft is typically a tapered tube made of metal or carbon fibercomposite. The golf club shaft has a given amount of flex. The shaftflex is the amount that the shaft will bend when placed under a load. Astiffer shaft will not flex as much, while a more flexible shaft will“whip” with less power required for better distance on slower swings,but may torque and overflex if swung with too much power causing thehead not to be square at impact, resulting in lower accuracy.

Typical current driver and fairway wood golf club heads are typicallyformed of lightweight, yet durable material, such as steel or titaniumalloys. These materials are typically used to form thin club head walls.The club head is joined to the shaft at a hosel.

The center of gravity configuration of a golf club head is a criticalparameter of the golf club's performance. Upon impact, the position ofthe center of gravity greatly affects launch angle and flight trajectoryof a struck golf ball.

Various approaches have been implemented for positioning discretionarymass, thus the center of gravity, about a golf club head. Many clubheads have integral sole weight pads cast into the head at predeterminedlocations to lower the club head's center of gravity. To achievelocalized mass, weights formed of high-density materials have beenattached to the sole, skirt, and other parts of a club head. Suchweights are usually permanently attached to the club head and arelimited in total mass. This fixes the club head's center of gravity.

Moreover, golf swings vary among golfers, but the total weight andcenter of gravity location for a given club head is typically set for astandard, assumed ideal, swing. Thus, even though the weight may be toolight or too heavy, or the center of gravity too far forward or too farrearward, the golfer often cannot easily find a club center of gravityto his or her particular swing. Rather, golfers often must test a numberof different types and/or brands of golf clubs to find one that issuited for them. Even then later fine adjustments of the center ofgravity would be desirable.

It should be appreciated that the ability to position and even adjustthe center of gravity location in the club head of golf clubs is usefulfor controlling performance of the golf club. It would be advantageousto have a system and process which facilitates selecting, positioning,and adjusting center of gravity.

SUMMARY

The present invention is directed to golf club apparatus and processes.A golf club with a center of gravity offset comprises a shaft presentinga central axis and a club head having a face and a hosel. The club headdefines a first axis generally parallel to the face and collinear withthe hosel. The shaft is joined to the club head at the hosel, with theshaft and hosel defining a second axis. The club head has a center ofgravity configured proximate the intersection of the first axis and thesecond axis.

These and other features, aspects, and advantages of the invention willbecome better understood with reference to the following description,and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a top view of an embodiment according to the currentinvention;

FIG. 2 depicts a side view of an embodiment according to the currentinvention;

FIG. 3 depicts a top view of prior art;

FIG. 4 depicts a side view of prior art;

FIGS. 5 a-5 c depict various configurations of the an embodimentaccording to the current invention;

FIG. 6 depicts club head speed and energy of data;

FIG. 7 depicts club head energy at various configurations of the currentinvention; and

FIG. 8 depicts an embodiment of a process according to the currentinvention.

DETAILED DESCRIPTION

Detailed descriptions of the preferred embodiment are provided herein.It is to be understood, however, that the present invention may beembodied in various forms. Therefore, specific details disclosed hereinare not to be interpreted as limiting, but rather as a basis for theclaims and as a representative basis for teaching one skilled in the artto employ the present invention in virtually any appropriately detailedsystem, structure or manner.

The center of gravity location in the club head 20 of golf clubs isuseful for controlling performance of the golf club. This means that aclub head 20 has a vertical center of gravity location, defined by theheight on the club head relative to the sole. It also has a horizontalcenter of gravity location, that is to say how far over it is from thecenter of the shaft 12 in the hosel 30 of the head. Finally, the centerof gravity is also defined by how far back from the club face it islocated.

Current drivers have the center of gravity behind the shaft 12attachment. This causes the shaft 12 to bend forward due to the forcecouple acting on the club head 20. The centrifugal force, the force upthe shaft 12, and the force in the opposite direction acting on the clubhead 20 center of gravity. This results in a bending moment turning theclub head 20 forward. The club head 20 rotates to the left (for a righthanded golfer) and upward, effectively giving a higher loft at impact.This forward shaft 12 bend is, in the golf industry, regarded as givingan extra “kick” to the golf ball, defining at a kick point of the shaft12, as shown in FIG. 3.

In further analysis of the shaft 12 kick, it is observed that thedownswing in a golf swing lasts approximately 0.02 seconds. During thistime the club head 20 moves about 50 mm forward relative where it wouldbe if the shaft 12 had been perfectly stiff (unbendable). Therefore, theaddition to the club head 20 speed is V=50 mm/0.02 s=0.05 m/0.02 s=2.5m/s=6 mph.

There is also another relevant effect, referred to as the “Hammer”effect in this specification. As the club head 20 makes contact with theball it will start to slow down. By observation and swing analysis dataof professional golfers, it is found that a typical club head 20pre-impact speed of 114 mph will result in a typical club head 20post-impact speed of 93 mph. The reduction in speed occurs over adistance of about 4/7 of the diameter of the golf ball. The diameter ofa golf ball is 43 mm. Therefore the speed of the club head 20 is reducedfrom 114 mph (51.0 m/s) to 93 mph (41.6 m/s) over a distance of 25 mm.As the speed is reduced, the shaft 12 will bend less at 93 mph than itdid at 114 mph. Let us again assume that a particular shaft 12 bendsforward by 50 mm at 114 mph. Assume the shaft 12 bends linearly with thebending forces, the bending forces are proportional to centripetalforces.

F=m×v ² /r

m equals mass and is constant. r equals radius and is substantiallyconstant, with the forward bend X at 93 mph. Therefore 114/93=50 mm/Xand X=33 mm.

Therefore the shaft 12 kicks backwards 17 mm (50 mm-33 mm). It does thisin the time it takes the club head 20 to travel a distance of 25 mm. Theclub head 20 is traveling at an average speed of (51.0+41.6)/2=46.3 m/s.The time taken is 0.025 m/46.3 m/s=0.0005 seconds=0.5 milliseconds. Thisis the duration that the club head 20 stays in contact with the ball.The speed decrease due to the Hammer effect is thereby 17 mm/0.5milliseconds, or 0.017 m/0.0005 s=34 m/s. The speed is decreasing due tothe Hammer effect, effectively linearly during impact. The effect shouldthereby be halved when calculating the effect it has on effective clubhead 20 speed. The average effective speed is thereby 34/2 m/s=17 m/s(38 mph)

In the example of the 114 mph club head 20 speed, the effect of theshaft 12 kick is accounted for. That means that in this example thegolfer is swinging the club at 108 mph (114−6), which will be furtherreferred to as the swing speed.

The shaft 12 kick is eliminated by selecting the club head's 20 centerof gravity to be located in line/collinear with the shaft 12, from thegolf club face 26 perspective, as shown in FIG. 1, where the club head20 presents a first axis generally parallel with the golf club face 26and collinear with the hosel 30. This can be accomplished by shiftingmore weight towards the face 26 of the club head 20 or by offsetting theshaft 12 attachment further towards the back of the club head 20, orcombination thereof. The club head 20 speed at impact would then be 108mph as there would negligible or no shaft 12 kick. However, theeffective club head 20 speed will be 146 MPH (108+38).

Assuming a given club, strike force, and swing speed of 114 mph the ballwill carry about 270 yards. Proportionately, a swing speed of 146 mphtypically yield ball carry of about 346 yards, or an increase indistance of about 76 yards.

As the shaft 12 will no longer bend forward or backward in the swingplane, a much higher degree of accuracy is obtained, leading to a morepredictable trajectory, that is to say that the ball will remain in thefairway as desired. As the shaft 12 kick is minimized or eliminated, theclub head 20 static loft and dynamic loft will be substantially thesame. For optimum results, the static loft of the club head 20 should beincreased as the static loft equals the dynamic loft. For a traditionalclub head, the dynamic loft is greater than the static loft. To accountfor this, a larger static loft is required when the static loft equalsthe dynamic loft. As the loft is increased, this give opportunity toposition more weight low and forward in the face of the club head 20,thereby facilitating alignment of the center of gravity with the shaftattachment to the club.

The further forward the center of gravity is located, the stronger theHammer effect. If one were to locate the center of gravity forward ofthe hosel 30, the Hammer effect would be even stronger as the club willkick forward at impact with the ball. The shaft 12 kick effect wouldthen be exhibited. This would have a small negative effect while thedominant effect will still be the Hammer effect. This will lead tofurther ball carry even, however accuracy will suffer again as the shaft12 flexes.

The shaft 12 flex can then be optimized by matching the frequency of thefully assembled golf club to the club head 20 speed of the golfer. Theoptimum club frequency for each swing speed can be obtained by testing.One frequency measuring method known in the art for obtaining the shaftfrequency of a shaft is to by locking the grip end of the shaft in avice and pulling the distal, free club head to the side and releasing itso that it can vibrate freely. A laser beam is used to count the cyclesover a time period and gives the resulting frequency in hertz. Thehigher the frequency, the higher the stiffness of the shaft. The higherthe frequency the faster the club head moves. It is within the scope ofthis invention to use other process or systems known to the art.

When a golf club is swung, the shaft 12 is bending, as the center ofgravity of the club head 20 is not aligned with the shaft 12. We arehere considering the bending in the plane affecting the dynamic lieangle, as illustrated in the adjacent space apart planes of FIG. 4. Thefaster the club is swung, the lower the dynamic lie angle at impactbecomes. This bending introduces a factor of uncertainty and causesirregular results. To compensate for this effect, the center of gravitycan be set inline with the shaft 12 line, as illustrated in the plane ofFIG. 2. The shaft is joined to the club head at the hosel, with theshaft and hosel defining a second axis. With this configuration ofcenter of gravity, the shaft 12 will not bend in any direction whenswung. The center of gravity of the club head 20 can be relocated bymoving masses when designing the club head 20 as well as by locating thehosel 30 in the required location.

Embodiments of the present invention are directed to method forselecting an optimum center of gravity, a golf club having a club head20 with an optimum center of gravity, and a golf club with a hosel body40 permitting user adjustment of the center of gravity of a club head20. Although the depicted hosel body 40 includes multiple hosels 30spaced apart, it is within the scope of this invention to include asingle hosel 30 at an offset with a configured center of gravity.

It is within the scope of this invention to apply the center of gravityto a newly created golf club or to apply the center of gravity offset toan existing club directly without the use of the above described hoselbody 40. FIG. 8 illustrates an embodiment of a process according to thecurrent invention. At step 110, the parameters for a golf club orsimilar golf clubs is received. Representative received parameters caninclude club type, shaft length, shaft thickness, club head weight, clubhead shape, club head composition, club face weight, club head weightdistribution, center of gravity position, hosel position, club faceposition, and other parameters. At step 120, the current center ofgravity of the club head is determined. It can be received directly ordetermined from the received golf club parameters. At step 130, theoptimum center of gravity is determined. The first axis of the club headgenerally parallel to the face and collinear with the hosel isdetermined. The second axis defined by the shaft joined to the club headis determined. The optimum center of gravity is determined and definedas proximate the intersection of the first axis and the second axis. Atstep 140, the optimum center of gravity is applied to the golf club. Anexemplary manner of doing so is by adding weighted screws to the clubhead 20. An alternate application of the process includes providing ahosel body 40 with a plurality of spaced apart hosels to be interposedbetween the club head 20 and the shaft 12, permitting user adjustment ofthe center of gravity of a club head.

Prior to play, a golfer may seek to adjust a club for directionaltendency (direction, as discussed above) or distance, seeking longer orsuperlong shots. For example, a course may have holes with open fairwaysand long tees, the golfer may seek a center of gravity which maximizesdistance. On the other hand, in a situation such as a tight fairwayswith “S” curves, directional control may be the higher priority. Thehosel body 40 includes an upper surface having a plurality of spacedapart hosels 30 disposed linearly. The exemplary hosels 30 are spacedapart with a range such that there is a hosel 30 position optimized foreach priority. As a golfer is not allowed, according to the rules ofgolf, to alter any club during play, in testing, practice, or othersituations, a golfer may adjust the center of gravity.

Testing was carried out with a golf club of the alternate applicationwhere the shaft 12 is offset at three different points defining threedifferent centers of gravity, as shown in FIGS. 5 a-5 c. Test data wasobtained using a Swingbyte measuring tool. The energy transferred to theball is calculated and shown in the figure below. Kinetic energy iscalculated as ½ mv², where m is the combined mass of the club head 20and the device for positioning the shaft 12 in three differentlocations, total mass is 388 g. club head 20 speed, v, before and afterimpact is obtained from the primary data from the Swingbyte measuringinstrument. Note that the device fixed to the club head 20 made the clubhead 20 very heavy. This caused a low swing speed. However, one skilledin the art would appreciate the indication of positive effect from thetrends shown the results. Raw test measurements are shown in FIGS. 6 and7.

Insofar as the description above and the accompanying drawing discloseany additional subject matter that is not within the scope of the singleclaim below, the inventions are not dedicated to the public and theright to file one or more applications to claim such additionalinventions is reserved.

What is claimed is:
 1. A golf club with a center of gravity offset, comprising: a shaft presenting a central axis; a club head having a face and a hosel, said club head defining a first axis generally parallel to said face and collinear with said hosel; said shaft joined to said club head at said hosel, said shaft and hosel defining a second axis; said club head having a center of gravity configured proximate the intersection of said first axis and said second axis.
 2. The golf club of claim 1 wherein the static loft of the club head is substantially equal to the dynamic loft.
 3. The golf club of claim 1 wherein weight is positioned lower and forward in the face of the club head.
 4. The golf club of claim 1 wherein the shaft flex is optimized by matching the frequency of the golf club to the club head speed of a golfer.
 5. The golf club of claim 1 wherein is the center of gravity of the club head is offset by moving masses.
 6. The golf club of claim 1 wherein is the center of gravity of the club head is offset by a configured hosel position.
 7. A process for golf club head center of gravity offset, comprising the steps of: receiving golf club parameters; determining the current center of gravity from said golf club parameters; defining a first axis generally parallel to the face of said golf club and collinear with the hosel of said golf club; defining a second axis defined by the shaft of said golf club to said club head at said hosel; determining the optimum center of gravity, said optimum center of gravity defined as proximate the intersection of said first axis and said second axis.
 8. The process of claim 7 further comprising the step of applying the center of gravity offset to said golf club.
 9. The process of claim 8 wherein said center of gravity adjustment is accomplished by shifting more weight towards the face of the club head.
 10. The process of claim 8 wherein said center of gravity adjustment is accomplished by offsetting the shaft attachment further towards the back of the club head.
 11. The process of claim 8 wherein said center of gravity adjustment is accomplished by a combination of shifting more weight towards the face of the club head and offsetting the shaft attachment further towards the back of the club head.
 12. The process of claim 12 further comprising optimizing the shaft flex by matching the frequency of the golf club to the club head speed of a golfer.
 13. A golf club accessory comprising: a hosel body having an upper surface and lower surface; said lower surface having a tip for affixing to a club head; said upper surface having a plurality of spaced apart hosels dimensioned for receipt of a shaft, whereby a user can selectively offset the center of gravity of the club head proximate the intersection of a first axis and a second axis, said club head defines said first axis generally parallel to the club face and is collinear with said hosel and said shaft and hosel defining said second axis. 